MAweatherboy1's Blog

96E May Develop; Atlantic Development Prospects for July

By: MAweatherboy1, 3:02 PM GMT on June 27, 2013

There is currently just one active tropical cyclone on Earth right now, and it is Tropical Storm Cosme in the East Pacific basin. Cosme was once a hurricane but is now dying over cold waters and stable air. It is badly decoupled, and will likely be a remnant low by tonight. It is not a threat to any land areas.


Figure 1: Tropical Storm Cosme

With Cosme out of the way, the focus turns to another disturbance in the East Pacific that has been designated Invest 96E. 96E is in a very typical location for East Pacific tropical development, a couple hundred miles off the coast of Mexico and the rest of Central America. 96E is currently disorganized and moving slowly northwest. Satellite images show a disorganized system, and the National Hurricane Center is only giving 96E about a 20% chance of developing in the next 48 hours. I think these are fair odds, as I don't foresee development in the next 48 hours due to its present lack of organization and marginal atmospheric conditions


Figure 2: Invest 96E.

Forecast for 96E
96E is in an area of moderate (15-20kts) wind shear, warm water, and a generally moist environment. The warm waters and moist atmosphere will favor development, while the current shear will be a limiting factor as shear generally needs to be little more than 10kts for an disturbance to organize into a tropical cyclone. The SHIPS intensity model indicates that shear is likely to drop to about 10kts within 24 hours, and then may fall very low between about 36 and 60 hours before picking up a little again. Depending on how well 96E does in the next 24 hours or so before shear drops, it may have an opportunity to organize fairly quickly when shear becomes more favorable. Several models are showing at least some development of 96E, and I would give it a 75% chance of ever becoming a tropical cyclone. Regardless of development, 96E is not a direct threat to land, though enhanced surf and rip currents will be a concern for the west coast of Mexico over the next few days. The SHIPS model shows a peak intensity of near minimal hurricane strength for 96E in 5 days. I am not really going to speculate on intensity at this point, since there are still questions as to whether 96E will develop at all, but I will say that a strong hurricane seems unlikely.

Atlantic Development Prospects for July
After two storms so far, the tropics are very quiet in the Atlantic basin right now, with no areas of interest and no development likely for at least the next 7 days according to the major global models. This is somewhat interesting, as an upward MJO pulse is expected in the Gulf and Caribbean within a week or two, which typically enhances moisture and can lead to tropical development. We have already seen the East Pacific affected by this MJO pulse as it helped form Cosme and 96E, which could become a tropical cyclone. The MJO by itself cannot cause development, however, so it looks like this pulse may bypass the Atlantic without causing development.


Figure 3: Areas with development potential before July 10- if something forms, it may end up being a storm similar to Barry.

With development fairly unlikely in the Gulf and Caribbean in early July, it would usually be likely that we would be looking at a very quiet July in the Atlantic, similar to last year, but that may not be the case. There are indications that more eastern areas of the Atlantic basin, usually off limits to development before the end of July, may get off to an early start this year. The CFS model has been fairly consistent in showing low pressure and storms in the Atlantic Main Development Region (MDR). The CFS is a climate model, and should never be used for the prediction of details of potential storms. It can, however, be used to determine how conducive an area may be for development, and since it has been showing storms and low pressure in the MDR, it can be inferred that an early start is possible for those types of storms this year. The GFS model, which can be used for individual storm details, has also been showing a steady train of waves off of Africa that would have the potential to develop. Currently, much of the East Atlantic is an area of high shear with stable air because of the dry Saharan Air Layer (SAL) coming off the west coast of Africa. This is normal for this point in the season, as shear and SAL typically do not fall to favorable levels for tropical development until late July and August. Tropical waves emerging off of Africa right now will act to erode the SAL, which will doom their chances of development, but pave the way for even stronger waves later in the season. The enhanced moisture from the coming MJO pulse will also work to erode the SAL.


Figure 4: Saharan Air Layer. Yellow/red areas represent areas with a concentration of SAL. A tropical wave can be seen eroding the SAL between 40W and 50W. Another weak wave is coming off of Africa now, and another strong wave can be seen at a slightly higher latitude heading for the African coast. You get the pattern- while these waves won't develop, the moisture they provide eliminates the SAL and prepares the east Atlantic for future development.


Figure 5: Area of possible development for mid-late July.

The last possible way a tropical cyclone could form in July is if something develops from non-tropical origins, for example a low pressure breaking off the tail end of a cold front and developing. These are completely unpredictable, but there is always a 30-50% chance of getting one every month. With all this said, here is my thinking...

70% chance of one storm
40% chance of two storms
10% chance of three or more storms
50% chance of a hurricane

As far as seasonal numbers go, I remain comfortable with my 15-8-3 prediction. I don't see any obvious reason to go lower as I am already below most predictions, but I don't see any reason to go higher either as there are no strong signs that this will be a particularly active season, especially with Atlantic instability still below average and ENSO trending more towards a warm neutral than a cool neutral. That is all for today; I don't expect to have a new blog up for a while since the tropics are pretty quiet (I may post an update on 96E if it develops), and I will likely be gone to Cape Cod for a few days around the 4th of July where I won't have Internet access. I hope you enjoy the rest of this month and have a happy 4th of July if I don't have a new blog before then.

MAweatherboy1

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TD 2 Reemerging Over Water; Leepi Disorganized in West Pac

By: MAweatherboy1, 1:27 AM GMT on June 19, 2013

There are currently two active tropical cyclones in the world right now, one in the Atlantic basin and the other in the West Pacific. The Atlantic cyclone is Tropical Depression Two (02L). 02L is currently located near the southeastern corner of the Bay of Campeche. After a trek across parts of Central America, the depression is clearly in poor shape this evening, and the National Hurricane Center (NHC) very nearly issued the last advisory on the storm at 5PM EDT today. Instead, they maintained it as a weak tropical depression with maximum 1 minute sustained winds estimated at a possibly generous 30mph and a minimum central pressure of 1007mb. 02L is moving generally WNW at about 10mph.


Figure 1: Tropical Depression 02L. The center is just now reemerging over water in the Bay of Campeche. Overall, the structure of the storm is quite poor, though a well defined center remains. Most of the deep convection over Central America is simply diurnal thunderstorm activity that is not related to 02L and should dissipate in the coming hours. The weaker convection farther north is in association with 02L.

Forecast for 02L
The reasoning behind the NHC maintaining 02L as a depression in the 5PM advisory is likely at least partially due to the fact that it is now moving back over the more favorable waters of the Bay of Campeche. This will give the system a brief, but non-zero opportunity to regain strength in the next 24 hours or so before it makes a final landfall on the far southern Gulf Coast of Mexico. A steady WNW motion is likely until landfall. The official forecast from the National Hurricane Center shows little change in strength during the system's time over water, as they intensify it slightly to 35mph tropical depression status. This is very much in line with my thinking. While there is some speculation that 02L may strengthen just enough to become Tropical Storm Barry, I find that less likely right now, as I think it probably has too much reorganizing to do in conditions that are only somewhat favorable for development. An aircraft reconnaissance mission is scheduled to investigate 02L tomorrow morning, if necessary. Regardless of development, locally heavy rains, flash flooding, and mudslides will be the main threat for areas impacted by this system.


Figure 2: Official NHC forecast for 02L.

Leepi Disorganized, Poses Minimal Threat
The other active tropical cyclone in the world tonight is Tropical Storm Leepi in the West Pacific basin. According to the latest warning from the Joint Typhoon Warning Center (JTWC), Leepi is currently located about 400 miles south of Kadena Air Force Base, and is moving northward at about 10mph. Maximum 1 minute sustained winds are estimated to be about 35kts or about 40mph, making it a minimal tropical storm equivalent.


Figure 3: TS Leepi, showing a large amount of disorganized deep convection. While it looks quite menacing, looks can be deceiving, as there is very little organization within the storm right now. The very warm waters of the West Pacific make it easy for many storms to fire off extremely deep convection.

Forecast for Leepi
Leepi is currently tracking northward along the western edge of a steering ridge. This should continue for about the next 24-30 hours. After that time, the shallow system will get caught in the strong prevailing westerly winds that so often dominate the northern part of this basin, which will cause it to accelerate, begin extratropical transition, and recurve east. This will bring it on a track that takes it fairly close to the south coast of Japan. The official forecast from the JTWC keeps Leepi offshore throughout its track. Meanwhile, the JTWC forecasts slight intensification to a peak of about 45kts between 24-36 hours out. This seems reasonable to me, as despite fairly favorable conditions Leepi will likely struggle to consolidate itself. I wanted to make my own track forecast but unfortunately ran a bit short on time tonight. However, I will say that looking at the models I think Leepi will have a tough time staying off of southwestern Japan, as it will likely not get caught in the westerlies until it is around that areas latitude. Therefore, I would expect a minimal Tropical Storm Leepi to likely come very close to making an official landfall or actually make a landfall in far southwest Japan in a little under two days. Impacts will be very minimal, with just some squally weather likely, along with enhanced surf and a rip current risk, which is likely the biggest threat.


Figure 4: Official JTWC forecast track for Leepi. As mentioned, I would favor a slightly more northerly track that brings a weak Leepi into or just offshore of southwest Japan late Thursday eastern time.

That is all for tonight. I thought about adding my thoughts on what to expect for the next couple weeks, but figured that can probably wait for a day or two. I am now on summer vacation (finally!!) so will have some extra time to blog and keep up on the tropics. Thank you as always for reading, and enjoy the rest of your week.

MAweatherboy1

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91L Disorganized but May Develop in Gulf of Mexico

By: MAweatherboy1, 12:35 AM GMT on June 04, 2013

With the 2013 Atlantic hurricane season now officially under way, the Atlantic is getting down to business, as there is already an invest knocking on the door of the United States. This disturbance, dubbed invest 91L, is currently located in the south central Gulf of Mexico. It is producing a very large but disorganized area of showers and thunderstorms, which are displaced well to the east of what would be considered the "center" of the system. This is indicative of wind shear, and indeed, 91L is currently in an environment of less than ideal atmospheric conditions for the formation of a tropical cyclone. According to the most recent ATCF update on 91L, it currently has winds of about 25kts and a pressure of about 1007mb. The National Hurricane Center is giving the system a 30% chance of development in the next 48 hours while it moves slowly northward.


Figure 1: Invest 91L, showing the disorganized area of convection well east of the center.

Forecast for 91L
As previously mentioned, Invest 91L is not in a particularly favorable environment for strengthening. The SHIPS intensity model is indicating 17-25kts of shear over the system for the next 24 hours, which will make organization slow at best. However, a window of opportunity may exist after this time for some development of the system. Multiple models are showing 91L developing at least a little, but the only major model to show significant strengthening is the CMC, which I have discarded from the development/intensity forecast due to its bias to overstrengthen tropical cyclones. Overall, I would give 91L a 30% chance of development within 48 hours, with a 50% chance of it ever developing, slightly higher than the 40% I have been thinking for the past 2 days or so. Models are in decent agreement on a general N/NNE track in the next few days. This should cause the system in whatever form it ultimately takes to come ashore at some point later this week. My thinking on track is shown in Figure 2. This is fairly high confidence and in good agreement with the models.


Figure 2: My thoughts on 91L.

Regardless of development, potential impacts from 91L will be the same. Heavy rainfall for the Yucatan, western Cuba, and Florida is likely in the next several days, along with some gusty winds. Development beyond a 45-50mph tropical storm is unlikely. Should this become a tropical storm, it would be named Andrea. Beyond its time in the Gulf, remnants of 91L may be drawn northward and affect the rest of the East Coast with rain and wind, though this is too far out to get into.

Elsewhere, the tropics are quiet throughout the world right now, with no imminent threats for development in any basin and none likely for at least the next 5 days. I hope to provide updates on 91L if necessary in the next few days. That is all for tonight; thank you for reading, and enjoy the rest of your week!

Updated: 12:57 AM GMT on June 04, 2013

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Two Year Anniversary of Springfield Mass. Tornado

By: MAweatherboy1, 2:18 PM GMT on June 01, 2013

Today is June 1, meaning it is the first official day of the 2013 North Atlantic Hurricane Season. Our wait in finally over! With the tropics fairly quiet this morning, however, I thought I would instead blog on another June 1 related topic that has become a matter of importance for me. Today is the two year anniversary of an EF3 tornado that touched down near Springfield, MA, killing three people, injuring about 200 others, and causing well over 100 million dollars in damage. The ingredients were all there that day, as extreme instability and strong shear associated with an approaching weather system. Tornado probabilities from the SPC were only at 5%, however, as storms were expected to be more linear than they turned out to be, producing a threat for mainly damaging winds as well as hail, with the possibility of brief tornadoes. This did not happen, however, and multiple supercells developed across Massachusetts during the day. One in particular began to develop in western MA near the CT border, and strengthened as it moved east through the favorable conditions. Radar began to indicate weak rotation, and by the time it reached western Springfield, a clear hook echo had developed, and rotation had intensified considerably, prompting a tornado warning at 4:17 PM EDT. As the tornado continued eastward, it tracked over Springfield and then heavily damaged the towns of Monson, Brimfield, and Sturbridge. A large debris ball became visible on radar for multiple frames, as debris was thrown high into the air and in some cases carried for dozens of miles. Finally, after being on the ground for about an hour and ten minutes, a path length of just under 40 miles, the tornado weakened and dissipated in the town of Charlton shortly before 5:30 EDT. A post storm survey of the damage indicated that this was an EF3 tornado with estimated winds of about 160mph. While not particularly uncommon in some parts of the country, a tornado of this magnitude is a very rare occurrence in Massachusetts. This was not the only tornado to touch down in the state on that day, but it was the strongest, as five other tornadoes were rated either EF1 or EF0, and they all caused mostly tree damage with some minor damage to structures.







My Personal Experience With This Tornado
I distinctly remember many of the events of June 1, 2011. It was a warmer than average, though not very hot day, with temperatures rising to the low 80s in my area, with humidity making it feel warmer and just to the point where it is slightly uncomfortably warm to be outside during the peak heat of the day. A few showers and storms moved through during the early-mid morning hours, but skies cleared quickly behind them. I had been looking forward to this day, a Wednesday, all week, as it was clearly our best chance of the year so far at severe weather, and it was also, of course, the official start of hurricane season. I was a high school freshman, and already plenty interested in tracking the weather, as I have been since I was very young. I was very excited to have a half day of school that day. After an 11:30 AM dismissal, I headed home, had a quick lunch, and settled in for the afternoon of watching the storms develop. One of my main questions would be whether the SPC would issue a tornado watch for my region or a severe thunderstorm watch. I knew a watch would be issued, but was unsure what kind it would be. My question was answered at 1:00 PM when tornado watch 411 was issued for portions of several Northeast and Mid-Atlantic states, including my county in MA. Storms were already strengthening and becoming severe at this time. I remember a tornado warning being issued for areas in far western MA around 3:30, and while this didn't amount to anything significant, it was a definite indication that tornadoes would be a threat this day. Before the tornado warning on the main storm was issued, I had already had my eye on it for a little while, partly because it looked like it might be in the best position to produce a tornado, and partly because I could tell it would be the storm most likely to affect my area, as it was moving almost due east, on a beeline for my area. I am always trying to wish severe thunderstorms into my area. I never want to see anyone get hurt, but as a weather enthusiast there's nothing better than watching a severe thunderstorm track right over you, especially when you don't get them too often like in my area. When the tornado warning was issued on the storm, I was excited. Soon, however, I realized what a serious situation this was, as live footage of the tornado in progress began to come into the local news stations, who distributed it to viewers like myself. My local TV meteorologists sounded very concerned as they watched the tornado signature strengthen on radar, and watched a classic debris ball form. My excitement was still very much present, but it was also mixed now with a touch of nervousness, as I could tell this was much more than a weak, brief tornado. It was doing real damage, and still on a path that would take it pretty much directly over my house. At 5:09 PM, with the tornado still clearly on the ground and doing damage, a new tornado warning was issued for Norfolk County, my county, as well as parts of Providence county in Rhode Island, to the south of me. (This turned out to not be a very well placed warning. The potential tornado ended up north of me, and certainly north of anywhere in RI.) An emergency broadcast went off on my TV (which I honestly found to be kind of funny), and my family members home at the time (Mom, two sisters, and my dog) actually had to prepare for the possibility that we would need to go to the basement soon. The warning was issued with considerable lead time for my area, so we didn't go down when the warning was issued. As I watched radar between the time of that tornado warning and 5:25PM or so, I began to gain confidence that this tornado would not hit my town for two reasons. One was that the storm took a bit of a left turn. The other was that the rotation was weakening, particularly after 5:20. The debris signature was dissipating, and the overall structure resembled one of a weakening supercell. The tornado dissipated quite rapidly shortly before 5:30PM. Of course, at the time, this was not known, and a tornado warning remained in effect as the storm continued to display some rotation as well as a bit of an appendage on its south/west side. As I noted above, the potential tornado ended up a bit north of me. I still received plenty of vivid lightning and thunder as this was still a severe supercell storm as it passed north of me. The full extent of the damage was not known until the next morning. My area had escaped, but areas just a little ways west had not, as some entire neighborhoods were badly damaged or destroyed, especially in Springfield, Monson, Brimfield, and Sturbridge. It is a day I will never forget for sure. I still wish for severe thunderstorms for my area, but am more cognizant of the fact that damaging tornadoes can and do occur in this region. Two years after this tornado, the affected areas have made huge strides on the road to recovery. Damaged or destroyed houses have been removed and rebuilt. Trees have been and continue to be replanted, as this storm hit multiple areas of dense and important forestland. There remain some evident marks of damage, and the work is not yet done, but the resiliency of the people affected has been impressive in the past two years, and with help from state and federal aid, many people's lives are returning to normal. This event definitely heightened the awareness of the general public up here to the tornado threat, and severe weather is always a lead topic on the news when it threatens.



Here is a link to the Wikipedia page on this storm, where some of the information/pictures in this blog came from. I would definitely recommend it if you want a little more detail on the storm.

Link

And here is an article from today.

Meanwhile, there is no severe weather in the forecast up here today; instead, we will be achieving our first official heat wave of the season as temperatures soar to over 90F for the third straight day. We will be close to that mark again tomorrow (perhaps a tad below) before a front moves through with showers and storms tomorrow night, bringing our temperatures back down closer to normal. As I type, the temperature has already risen to 86F by 10:15 AM.

That's all for today. Thank you for reading; I hope you found this informative. Have a great weekend, and happy hurricane season!

MAweatherboy1

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About MAweatherboy1

Just an average 18 year old weather nerd. I work as an observer at the Blue Hill Meteorological Observatory in Milton, MA.